The present invention is directed to an impact cushioning means utilized to cushion impact forces generated at the end of a stroke of a fluid pressure actuated motor employed to actuate an article gripping or clamping device.
Fluid pressure actuated clamping or gripping devices of the type with which the present invention is concerned are widely employed in large numbers on automated article or part handling machines to releasably grip and position a part or workpiece at a work station or to transfer a workpiece to or from a work station. These clamps or grippers typically include a fluid pressure actuated cylinder-piston type fluid motor whose piston rod is coupled by a linkage to pivot one or both of a pair of part gripping jaws between a closed part gripping position and an open part release position. In the usual case, the motor is pneumatically actuated via a four-way reversing valve so that the piston of the motor is driven in a forward or reverse stroke by full line pressure. When the piston is driven in a forward stroke, it drives the jaws to their closed position to grip the part and the forward end limit of movement of the piston is established when the part is gripped between the jaws of the device. In the case of a gripper of the type in which a pointed projection on one of the jaws is partially embedded into the workpiece to lock the workpiece against lateral displacement, the impact forces generated by closing of the jaws have a functional purpose and are acceptable.
Normally, upon opening of the jaws it is desired to have the jaws open as wide as possible to provide maximum clearance for moving the part to and from operative relationship with the opened jaws. Thus, the full stroke of the piston is normally utilized during the return or jaw opening stroke and the rearward end limit of movement of the piston typically is established by the engagement of the piston with the rearward end wall of the piston chamber. Impact at this end of the piston stroke accomplishes no useful purpose, and it is quite conventional in the prior art to mount a resilient cushioning member or bumper on the rearward face of the piston to cushion its impact with a stationary surface of the cylinder housing at its rearward end limit of movement.
While such piston mounted bumpers normally have a reasonably long service life, eventually they must be replaced, and replacement requires disconnecting the motor from its pressure source and disassembly of the motor to a point where the rearward end face of the piston is accessible for removal and replacement of the bumper.
The present invention is directed to a cushioning device for a fluid pressure actuated clamp or gripper which may be inspected or replaced without requiring disconnection of the motor from its pressure source or disassembly of the motor itself.